I mean, will i even have gold for basic skills etc
As any class, you should have enough as long as you don't waste money on anything other than food and repairs.
A lot of of your talents wont need to be upgraded past rank 1, whether because they don't gain much from the upgrade (intercept/shield bash) or because you wont use them much (rend, TC, shouts)
are mobs are really so difficult to kill as you say?
Depends on your gear, but it's rough. With an unlucky string of misses/parries/etc it possible to die to a mob of same level.
It get's better as you level up, I'd say first 30 levels are the toughest. Strongly recommend doing as many dungeons as possible to keep your gear up to date.
And are warriors are the only tanks in vanilla?
They are for raids, for 5 mans anything works if you have good group.
Druids lack gear and CDs to compete with warriors and pallies lack taunt and run out of mana too fast.
My main focus will be to play pvp. How he deals with mediocre gear vs other classes who also have mediocre gear?
https://www.youtube.com/watch?v=NXX8URSUWm0Are they really so hard and tiring to play solo?
I would say yes, but I'm sure some will disagree.
Kill 1-3 mobs, eat, repeat.
In wotlk i just went protection tree and killled 10 mobs at once
You'll have problems killing 2 mobs at once.
Prot does very little damage and offers very little survivability.
There are some prot leveling specs that focus on stuns that some people claim to work well, but I haven't tried those.